<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>

        <style>
            h1{color: aquamarine}
        </style>
        <!--css引入方式-->
        <link rel="stylesheet" href="my.css">
    </head>
    <body>
        <h1 style="color: black">内联样式1</h1>
        <h1 style="color: gray">内联样式2</h1>

        <h1>内联样式1</h1>
        <h1>内联样式2</h1>
        <h1>内联样式3</h1>

        <h3>外部样式1</h3>
        <h3>外部样式2</h3>
        <h3>外部样式3</h3>
    </body>
</html>